1. Field of the Invention
The present invention relates to a luminaire using a light-emitting element such as a light-emitting diode as a light source.
2. Description of the Related Art
A light-emitting diode has been increased in the light-emitting efficiency, and used as a light source. A lighting apparatus using a light-emitting diode as a light source has been commercialized as a relatively large lighting apparatus for home and office use. Jap. Pat. Applin. KOKAI Publication No. JP2008-257903 discloses a lighting apparatus comprising square panels having light-emitting diodes arranged in a checkered pattern on a ceiling. Jap. Pat. Applin. KOKAI Publication No. JP2002-117705 discloses a lighting apparatus, in which a main unit is recessed in a ceiling. This lighting apparatus comprises a main unit recessed and fixed to a ceiling, and a panel-like light source unit fixed to the side frame of the main unit with a hinge having a rod. The light source unit comprises a large number of white light-emitting diodes. Jap. Pat. Applin. KOKAI Publication No. JP2001-005409 discloses a displaying apparatus, in which a large number of displaying units using light-emitting diodes as a light source is recessed in the ceiling of arcade.
The above lighting apparatuses are reduced in weight by making a main body a thin panel by using a light-emitting diode as a light source. Since the installation operation of the lighting apparatus on a′ ceiling is required to perform in high places, the operation is difficult. Therefore, it is important to simplify the installation operation. Further, in the lighting apparatus disclosed in Jap. Pat. Applin. KOKAI Publication No. JP2008-257903, as described in paragraph [0011], the panels are installed on the ceiling by using a fixing means such as a screw, which must be removed on maintenance. Thus, the installation operation includes troublesome steps, and the lighting apparatus may not be securely installed.
As for the lighting apparatus shown in Jap. Pat. Applin. KOKAI Publication No. JP2002-117705, according to the description of paragraph [0007] and [0008], the main unit is fixed to a edge of opening on a ceiling by a common method using the elasticity of spring material. Thus, if the main unit assembled with a lighting unit is very heavy, the lighting apparatus may not be securely installed. Particularly, if the lighting apparatus is very large, the equipment may not be supported by sufficient strength. When the equipment is installed on a ceiling, the equipment is fixed to the edge of opening on the ceiling in the state in which the panel-shaped light source unit is previously fixed to the main unit. The installation operation is difficult, because the operation must be performed while supporting a relatively heavy part such as the light-emitting unit. Though a light-emitting diode is adopted as a light source, workability is not improved. Therefore, improvement of the installation operation is required.
Generally, a large-size lighting apparatus uses a large number of light-emitting diodes. A large number of lead wires connecting the light-emitting diodes to a power supply unit are liable to complexly extend. Therefore, it is important that how to connect the lead wires, how to prevent interference between a light-emitting diode and a light source unit, and how to prevent breaking of wire. In the lighting apparatus disclosed in Jap. Pat. Applin. KOKAI Publication No. JP2001-005409, according to the description of paragraph [0007], a large number of lead wires are connected in vertical and horizontal directions. The electrical wires and lead wires of the light-emitting diodes are exposed to the rear side of the light-emitting unit And disturb the installation of the lighting apparatus. Something may contact and damage or break the electrical wires. Owing to the structure, this lighting apparatus is difficult in reducing the size, and the workability in installation is not improved.
Further, in the lighting apparatus described in Jap. Pat. Applin. KOKAI Publication No. JP2001-005409, according to paragraphs [0021] and [0022], two or more panel-shaped lighting units are arranged and fixed to supporting wires. The lighting units are not connected to one another. Thus, clearance is likely to occur between the lighting units. In the lighting apparatus comprising two or more light-emitting units, if a clearance is present between adjacent light-emitting units, light may leak from the clearance. Therefore, the lighting apparatus comprising two or more light-emitting units is required to have a structure causing no clearance between adjacent light-emitting units.